The present invention relates to a process for forming thin film wiring patterns on a dielectric substrate. In particular, the present invention relates to a process for selectively applying metallization by an electroless plating method.
Semiconductor packaging technology has progressed beyond the simple dielectric substrates due to the speed and dimensional requirements of advanced devices. These dielectric substrates may be organic in nature such as the conventional epoxy/fiberglass printed circuit boards or the more advanced sintered inorganic dielectric substrates having co-fired metallurgy. The use of thin metallized layers of organic dielectrics (so-called thin film layers) has become widely accepted as the solution addressing the new technological requirements. Ideally, the underlying dielectric substrate provides the interconnection capability for mating with the next level of packaging, the basic power supply wiring, and a metallized top surface for supporting multiple organic signal wiring layers. Structures have been proposed having multiple thin organic layers with associated signal metallurgy on the top surface of the dielectric substrate. However, the fabrication of multilayer metallized organic structures is difficult to achieve using the processing techniques which are standard in the semiconductor and package processing industries.
Challenges to fabrication of a multilayer organic structure include adhesion of the polymeric material to both the associated metallurgy and the subsequently-deposited layers of polymeric material. The adhesion, the mechanical integrity and the electrical integrity of an organic layer can be influenced by the amount and type of processing to which it is exposed. Therefore, it is desirable to minimize the processing of the multilayers in order not to compromise the properties of the materials and thereby the mechanical and electrical integrity of the structure.
Typical multilayer organic structures utilize multiple high vacuum metal sputtering and photolithographic operations to define the wiring metallization. These complicated operations contribute to the lengthy raw cycle time to complete a structure and the low yields obtained. The use of electroless plating operations has the potential for significantly reducing the number of process steps and capital costs associated with metallization. However, the full impact of the electroless plating approach can only be realized by being able to selectively plate only those regions where metallization is desired
Accordingly, it is a purpose of the present invention to have a process for forming an organic structure, which may be a multilayer structure, in which the number of processing steps is reduced.
It is another purpose of the present invention to have a process for forming an organic structure wherein adhesion is promoted between the metallization and the organic material.
It is a final purpose of the present invention to have a process for forming an organic structure wherein the metallization is selectively deposited by an electroless plating procedure.
These and other purposes of the invention will become more apparent after referring to the following description considered in conjunction with the accompanying drawings.